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Science

Advances in electrical devices

Types of batteries

There are two main types of battery: non-rechargeable batteries and rechargeable batteries.

Non-rechargeable batteries

Ordinary 'dry-cell' batteries are non-rechargeable. As the reactants inside them become used up in chemical reactions, the output from these batteries gradually falls. Once all the reactants have been used up, these batteries go 'flat' and cannot supply electrical energy anymore.

Rechargeable batteries

Rechargeable batteries usually maintain a constant output until just before they go flat. They contain reactants that can be made again just by passing electricity through the products. Once the battery has gone flat, it can be connected to a recharger. This uses electrical energy to reverse the chemical reactions that happened in the battery while it was in use.

Car batteries are rechargeable batteries - they are constantly recharged while the car is moving, so the lights and horn will always work.

Mobile phones, many MP3 players and other portable devices use rechargeable batteries. They must be recharged at regular intervals. It is usually recommended that such batteries should almost be flat before recharging. This allows the battery to be fully charged again.

Which is best?

Advantages and disadvantages of rechargeable and non-rechargeable batteries

non-rechargeablerechargeable
cheap to buyoften expensive to buy
can only be used oncecan be used many times
expensive to use in the long run as more are needed (high cost / performance ratio)cheap in the long run as they can be re-used (low cost / performance ratio)
output falls gradually with timeoutput stays constant until almost flat
disposal of many batteries creates a lot of chemical pollutiondisposal of fewer batteries creates less chemical pollution

Watch

You may wish to view this BBC News item from 2006 about recycling old batteries.

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